CUNNINGHAM, KEVIN J., Department of Geology, The University of Kansas, Lawrence, KS; and *EVAN K. FRANSEEN, Kansas Geological Survey, Lawrence, KS

ABSTRACT: Hierarchial Ordering of Depositional Sequences in an Upper Miocene Carbonate Complex, Cap des Trois Fourches, Northeastern Morocco

An Upper Miocene carbonate complex is dramatically exposed over a 4 km x 7 km area in coastal cliffs and inland canyons at Cap des Trois Fourches, northeastern Morocco, providing an excellent opportunity to study hierarchial ordering of depositional sequences. Three hierarchial orders of magnitude of depositional sequences have been identified (1DS-3DS). The entire carbonate complex is composed of two relatively low-order depositional sequences (1DS<1>, 1DS<2>). The oldest depositional sequence (1DS<1>) is composed of at least 6 higher order depositional sequences (2DS<1>-2DS<6>). The 3 lowest depositional sequences (2DS<1>-2DS<3>) form a 100+ m-thick transgressive deposit of bryozoan, red-algal and lithoclastic packstones and grainstones onla ping a major unconformity on Paleozoic metamorphic rocks and Tortonian silty marls. This unconformity forms the basal sequence boundary of the carbonate complex. Two overlying depositional sequences (2DS<4>, 2DS<5>), 50-60 m thick, downlap onto 2DS<3> with off lapping clinoforms of bivalve grainstones that grade basinward into marls. Overlying 2DS<5> is a dolomitized fringing-reef complex (2DS<6>), up to 80 m thick and 1 km wide, composed of reefal and bioclastic clinoforms that prograded with gradual downstepping basinward. The fringing-reef complex contains at least nine even higher-order (10's of m) depositional sequences (3DS<1>-3DS<9>). A second low-order sequence boundary, related to Mediterranean sea drawdown during the Messinian Salinity risis, is expressed as an erosional unconformity on top of the fringing-reef complex. This sequence boundary is onlapped by a second low-order depositional sequence (1DS<2>) composed of sandstones and peloidal, oolitic and stromatolitic carbonates that are locally up to 60 meters thick.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.